A Polish priest has warned parents to be on their guard against Lego, warning the plastic blocks are a tool of Satan and can "destroy" children's souls.

In a presentation aimed at parents, Father Slawomir Kostrzewa said the popular Danish toy company had taken a lurch to the dark side with its series of Monster Fighters and Zombie mini-figures, and that they "were about darkness and the world of death".

"Friendly fellows have been replaced by dark monsters," he explained. "These toys can have a negative effect on children. They can destroy their souls and lead them to the dark side."

Lego's Monster Fighters range features Lord Vampyre, a fanged Dracula-like character, who battles the likes of Doctor Rodney Rathbone and Major Quinton Steele as they try to prevent him from "cloaking the world in darkness".

The priest also cited research by New Zealand's University of Canterbury that found the facial expressions of Lego figures have also become angrier over the years, and that this compounded their evil potential.

"Facial expressions may be lead to confusion between good and evil," said Father Kostrzewa. "It appears the good suffer in battle and the 'villains' have a face showing satisfaction with their evil deeds."

But the claims that Lego blocks are becoming the work of the devil was dismissed by at least one expert.

"These are just blocks," retorted Monika Filipowska, a psychologist interviewed by the Super Express newspaper. "Linking them to Satan is just wrong, and all that will happen is that children will be afraid of them now."

Father Kostrzewa's attack on Lego is not the first time he has accused toys of harbouring evil. Hello Kitty and My Little Pony have also come under his scrutiny, with the latter being described as a "carrier of death".